LAUSR

The use of antibiotics in animal feed, commonly used as a strategy to achieve greater daily weight gains and recently as way to reduce methane emission, might result in the selection of resistant microorganisms and certain bacterial strains isolated from cattle are resistant to multiple antibiotics and could be human health hazards. To evaluate methane production in ruminant diet without roughage containing ionized amino acids as antibiotic alternative, twenty-four Nellore young bulls were allotted into two groups. The first group was fed with high-grain diet without roughage and without antibiotics diet, containing 82 mg/kg of ionized amino acids mixture (L-lysine and L-taurine HCl 99%, pH 9.74) manufactured by MJ Animal Nutrition. The second group was fed with high-grain diet containing Brachiaria brizantha hay (15% dry matter) and sodium monensin (120 mgּּ animal -1 ּּ day-1). It was not used a negative control group to avoid metabolic disturbances. The feedlot time was 100 days. The weight measurements were performed at the beginning of the trial period and monthly, always with water restriction and fasting for 18 hours, even before slaughter. A completely randomized design was used. Methane emission was measured using the sulfur hexafluoride technique and daily dry matter intake were measured in GrowSafe system. There was no detection of lameness or laminitis in any groups and there were no changes in feed conversion ratio (FCR). The total methane emission (-77.11%) and the methane emission per dry matter intake (DMI; -57.12 %), per average daily weight gain (ADG; -71.11%) and per kilogram of carcass (-70.07%) were different between treatments (P < 0.0001), resulting in decreased emission intensities for group fed without roughage with diet containing ionized amino acids. We conclude that fed without roughage with diet containing ionized amino acids was an effective strategy as an antibiotic alternative, mitigate GHG emissions and facilitate feedlot diets management. In field conditions, the roughage-lacking diets represent advantage, especially regarding its administration to a large amount of the animals just once a week or less, no need area, infra-structure and expertise to produce, preserve and feeding roughage.